In the receiving stations, after finishing and complete ejection of the waste, separation of the blanks consists in breaking the points of attachment between the blanks of a sheet by means of a male upper tool and a female lower tool mounted vertically above one another in the region for receiving sheets. The upper tool is formed by pusher elements which are slightly smaller than the periphery of the blanks. The lower tool is formed by a grid in which the shape of the openings generally corresponds to the periphery of the blanks. The blanks drop through these openings and are piled up in vertical stacks in the receiving region.
In order to form separated and stable stacks of blanks below these tools and on the receiving pallet of the station, periodic insertion of a stabilizing sheet has proven necessary. The insertion consists in arranging an insert sheet, such as a full sheet, between usually successive stacks of blanks. To perform this insertion without requiring a concomitant stopping of the production unit, a device commonly referred to as a non-stop receiving grid is used.
To perform an insertion operation, an insert sheet is grasped from a stack of insert sheets arranged in the vicinity of the receiving region. The insert sheet is then released onto the non-stop blank receiving grid. The non-stop receiving grid bearing the insert sheet is then moved below the lower tool for separating the blanks. The non-stop receiving grid then returns blanks above the stack of insert sheets to receive a new sheet. When leaving the receiving region, the grid crosses the teeth of a comb which has pivoted into the retaining position to retain the insert sheet and thus the blanks stacked on this insert sheet in the receiving region. The non-stop receiving grid thus makes it possible to deposit an insert sheet between the stacks of blanks and to support the blanks during the removal of the stacks of blanks without stopping the production.
Also known is a loading device provided with a mobile plate for performing only the insertion operations, with the support of the blanks during the removal of the stacks without stopping the production being provided by other means.
In order not to lower the quantity of blanks produced, the movement of the grid or of the plate bearing the insert sheet toward the receiving region must be carried out quickly in order to interleave the insert sheet between the last blank deposited on the top of the stack and the next blank as quickly as possible. Given the relatively large travel to be performed and the high production rates which can require movement speeds of the order of 1 m/s for the grid or the plate, it has proven to be difficult to maintain the insert sheet in position. In particular, the accelerations and decelerations may be too sudden to correctly drive the insert sheet. It may occur that, on its arrival in the receiving region, the insert sheet is offset or oriented awry and is thus poorly positioned between the blanks of the stack.